278 
THE ART OF REARING 
the red colour becomes ashy and white. This disorder does 
not always kill the worm in the first moulting-, nor yet in the 
second ; and sometimes they do not die until after the fourth 
moulting or casting of the skin, when they have uselessly 
consumed a quantity of leaves. When they live so long, it 
becomes more difficult to distinguish, as their colour becomes 
less dark and remarkable, and they cannot so easily be sepa- 
rated from those that are healthy, and might be mistaken by 
the most practised eye. They will even attain as far as rising 
on the edges, and weave cocoons which are good for nothing, 
which arc vulgarly called cafignons, from being soft and ill- 
woven. 
Of the Vaches, Gras, or Yellows. 
Some authors divide this disease into three classes, but -the 
specific characters which they give of them do not appear to 
me sufficiently marked to induce me to be of their opinion. 
It may be that a difference of names in various provinces may 
have caused this division of one disorder into three classes. 
And in one province, it may be further stated, a disorder may 
present circumstances which it will not offer in another pro- 
vince. But still I persist in thinking, that these classes are 
only modifications of one disease. The following are the true 
and essential characteristics of this disorder : — 
1st. The head of the worm swells. 2nd. The skin is drawn 
tight over the rings, and shines as with varnish. 3rd. The 
rings swell. 4th. The circumference of the aperture of the 
stigmates is of light or deep yellow colour. 5th. And the 
worm voids a yellow liquid which may be seen on the leaves. 
This disease generally appears tow'ards the second cast, or 
moulting, rarely later, and is scarcely known in the fourth 
age. M. Constant du Castelet, one of the earliest and best 
writers on the management of silk-worms, attributes this 
sickness to an acid and viscous liquid which penetrates the two 
reservoirs attached to the sides of the insects, and which mix- 
ing with the gum of which they are to spin their silk, impedes 
the progress and consummation of this gum, and causes a gene- 
ral distention in the insect, which makes it stretch its feet : 
it soon after becomes soft, contracts, and then bursts upon 
